Rubber tire



Patented July 21, 1931 UNITED STATES PATENT OFFICE RUBBER TIREApplication filed August 31, 1929, Serial No. 389,818, and in GermanySeptember 8, 1928.

My present invention relates to rubber tires for the wheels of vehiclesand particularly to theforin of the cross-section of such tires.

I have ascertained and verified beyond doubt, both by theoreticalcalculations and practical tests, that, in the case of a rubber bodystressed under pressure, the form of the two boundary surfaces whichintersect the direction of the pressure (i. e. the inner and Outerperipheral surfaces) must be such that they converge relatively to eachother so that pressure will be uniformly distributed over the whole ofthe stressed cross-section of the rubber body. In this respect theworking 5 material, rubber, does not differ radically from other similarmaterials, but as a result of its higher elasticity both the boundarysurfaces in question which take up the stress directly are, according tothe invention, pro- 26 vided with a form which deviates fundamentallyfrom the forms hitherto in vogue and of which the characteristic featureis that the outer tread or running surface, starting from the lateraledges or walls of the tire and as far as the middle of the tire, ap

proaches towards the inner or carrying surface, and so that the latterextends towards the tread surface both at the middle of the tire andalso at the edges of the tire. The ob- 30 truding points or vertices ofthe inner or supporting surface lie nearer to the vertical central planeof the tire than the obtruding points or vertices of the tread surface.If the rubber tire, according to my invention has to be. provided withcavities, ar-

ranged in a known manner symmetrically with respect to the verticalmiddle plane of the tire, each cavity is constructed so that its wallswhich meet at a point in the interior w of the tire, extend more or lessparallel to the lateral faces or walls of the tire and so that theoutermost cavity walls are outside the vertices of the under surfacesupporting the tire or else substantially coincident therewith. It hasbeen found that the wear on the tread surface of a rubber tire formedaccording to the present invention is uniformly dis tributed over theentire periphery of the ti re and that the wear in consequence is merelya fraction of the wear which has hitherto been unavoidable in rubbertires. A further result of the uniform distribution of pres sure overthe Whole tire cross-section is that no bending out or other similardeformation in the lateral walls of the tire is produced by the pressurestress.

It has already been proposed to employ a peripheral groove in the middleof the tire so as to increase the resistance of the running surface toskidding. However, such a groove does not increase the wearing andelastic properties of the tire unless its entire cross section is formedin accordance with the present invention only in the latter case is auniform distribution of the pressure stress over the entirecross-section of the tire attained.

In the accompanying drawings the three figures are axial cross-sectionsof different embodiments of the invention.

In the example diagrammatically illustrated in Fig. 1 the tire has across-section of which the tread or running surface, from the lateraledges or walls of the tire to the middle of the tire converges sharplyat (1 towards the inner or supporting surface (compare the tread surface7 cl and f d). Furthermore the supporting surface rises towards thetread surface in the middle plane of the wheel (that is, at 7L), andalso at the tire edges (nan1ely,from the obtruding points or vertices eand 6 towards 72, and h The vertices e and e of'the supporting surfacearepositioned nearer to the middle plane of the tire than thecorresponding vertices and f of the running surface.

In Fig. 2 there is shown a constructional form of tire provided withcavities.

The tire is mounted by a vulcanizing process on a rigid felloe g madeupof severalparts. The cavities are distributed symmetrically about thecentral plane of the tire in known manner. The walls 71 11 of eachcavity meet at points i in the interior of the tire and extend indirections more or less parallel to the walls h f and runningsurfaces f(Z of the tire respectively. No unfavourable effect is thus produced onthe uniform distribution of pressure over the entire cross-section ofthe cavities illustrated. It has also been found that, for the samepurpose, it is necessary that the outer walls i 7: of the two cavitiesshould cross the vertices of the carrying surface (compare 0 and e inFig. 1) or terminate outside these vertices.

On the other hand the walls 2', i of the two cavities may be more orless inclined to each other. depending upon the elasticity requirementsfor the tire. In Fig. 3 there is shown a tire in which the walls f (Zand (Z 7 of the running surface are flatter than in the constructionalforms shown in Figs. 1 and 2. Hence, in this case the walls 71 and i ofthe cavities now join each other in a correspondingly modified mannerand the central supporting wall between the two cavities is dispensedwith entirely.

lVhat I claim as my invention and desire to secure by Letters Patent ofthe United tates, is:

1. A resilient tire for vehicle wheels having a tread surfacereentrantly U-shaped in cross section to provide two lateral vertices,and an inner or supporting surface which rises toward the tread surfaceboth at the middle and adjacent the lateral faces of the tire andproviding two vertices, the radially inner vertices on the inner orsupporting faces of the tire lying nearer to the central plane of thetire than the radially outer vertices of said outer surface.

2. A rubber tire for a vehicle wheel having a tread surface reentrantlyV-shaped in cross section, and providing two laterally disposedvertices, the inner or supporting surface of the tire being formed witha cavity, the walls of which extend toward the tread surface, the treadsurface on each side of the cavity extending laterally and outward, theinner surface of the tire thus having two vertices, the vertices of theinner surface lying nearer to the medial radial plane of the tire thanthe vertices of the tread surface.

3. A rubber tire for vehicles having a reentrantly t -shaped treadsurface, thus providing two lateral vertices, the side faces of the tireextending downward and outward from said vertices. the inner face of thetire being provided with a medially disposed cavity and laterally ofsaid cavity the inner face of said tire extending laterally and outward,the lateral walls of the cavity being approximately parallel to thelateral walls of the tire, the lateral walls of the cavity substantiallycoinciding with the vertices on the tread of the tire.

l. A tire for vehicle wheels having its tread surfaces reentrantly Vshaped to provide two lateral vertices, the side faces of the tireextending inward and laterally outward from said vertices, the innerface of the tire from the inner corners of the lateral faces extendingcentrally inward and toward each other to points inward of theradialplanes of said outer vertices, to thus form inner vertices, the innerface of the tire being formed with a cavity between the vertices of theinner face.

5. A tire for vehicle wheels having its tread surface reentrantlyV-shaped to provide two lateral vertices, the side faces of the tireextending inward and laterally outward from said vertices, the innerface of the tire from the inner corners of the lateral faces extendingcentrally inward and toward each other to points inward of the radialplanes of said outer vertices, to thus form inner vertices, the innerface of the tire being formed with a cavity between the vertices of theinner face, the lateral walls of said cavity being approximatelyparallel to the side faces of the tire, the outer wall of said cavityextending downward and inward convergzently toward the medial radialplane of the tire.

In testimony whereof I affix my signature.

LUDWIG I-IARTER.

